To characterize cardiovascular adaptation to moderate and strenuous exercise stress in miniature swine, we will measure hemodynamic parmeters, disribution of cardiac output, regional blood flow in the myocardium, and coronary collateral development as well as assess various biochemical and morphologic changes. Evidence from skeletal muscle suggests that cardiovascular adaptations associated with exercise stress may result from increased myocardial perfusion, from a more efficient utilization of oxygen and substrate, or from a combination of these. Our experimental design will control such variables as age, diet and life style and will quantitate exercise workload, allowing us to isolate the effects of exercise stress on functional and structural adaptations of the healthy heart. Once these adaptive changes are understood, similar studies of cardiovscular adaptation in other forms of physiologic or pathologi stress, such as chronic work overload or hypertension, may be undertaken. If similar mechanisms are involved this knowledge may lead to a more rational approach to effective therapy.